A sty is a small, painful red bump that forms on the edge of your eyelid, usually caused by a blocked oil gland or a minor infection. It looks like a tiny pimple right where your eyelashes grow, and it can make your eyelid feel sore and swollen. Most sties go away on their own after a few days.

The word also means an enclosed pen where pigs live on a farm. A pigsty provides shelter for pigs, with walls or fences to keep them contained. While pigs are actually quite clean animals when given proper space, their sties can get muddy and messy. When someone says their room looks like a pigsty, they mean it's extremely messy and disorganized, with stuff scattered everywhere. “Clean up this room! It looks like a pigsty!” a frustrated parent might say when confronted with dirty clothes on the floor, an unmade bed, and yesterday's snack wrappers under the desk.